The present invention relates to a process for producing a chip and a pressure sensitive adhesive sheet for producing chip. More particularly, the present invention is concerned with a process for producing small chips such as semiconductor chips in which chip spacings can be expanded without the need to conduct the conventional expansion step and a pressure sensitive adhesive sheet for producing chip suitably employed in this process.
A semiconductor wafer of, for example, silicon or gallium arsenide is produced in a large diameter, cut and separated (diced) into elemental chips and subjected to the subsequent mounting step. In this process, the semiconductor wafer undergoes dicing, expansion and picking-up steps in the state of being attached to a pressure sensitive adhesive sheet and is transferred to the subsequent mounting step.
In the expansion step, the pressure sensitive adhesive sheet is extended so that chip spacings are expanded. The objective of the expansion step in which chip spacings are expanded is to facilitate chip recognition in the die bonding and to prevent device breakage attributed to abuttal of neighboring chips in the pickup step.
Currently, the expansion step is carried out by extending the pressure sensitive adhesive sheet with the use of an expanding apparatus.
In most expanding apparatuses, the degree of extension and the torque during the extension are fixed to thereby render difficult adjusting dependent upon the type of pressure sensitive adhesive sheet and the size of device.
Accordingly, it has occurred that, when the pressure sensitive adhesive sheet is soft, the extending stress is not conveyed to the object setting portion to thereby disenable attaining satisfactory chip spacings and that, on the other hand when the pressure sensitive adhesive sheet is hard, the torque of the apparatus is unsatisfactory or the pressure sensitive adhesive sheet is torn.
Further, when the die bonding is completed, the pressure sensitive adhesive sheet is housed, in the state of being set on a ring frame, into a ring frame cassette. In the conventional process, the pressure sensitive adhesive sheet having been deformed by the expansion must have its shape restored to the original by the use of hot air. When the restoration of the shape is unsatisfactory, the pressure sensitive adhesive side of the pressure sensitive adhesive sheet occasionally adheres to the ring frame cassette to thereby disenable housing thereof. Thus, an automization has been difficult.
The present invention has been made with a view toward resolving the above problem of the prior art. An object of the present invention is to provide a process for producing a chip in which chip spacings can be expanded according to mechanism which is radically different from the conventional expansion method, and another object of the present invention is to provide a pressure sensitive adhesive sheet for producing chip suitably employed in the above process.
The process for producing a chip according to the present invention comprises the steps of:
setting an object to be diced on a pressure sensitive adhesive sheet for producing chip comprising at least one layer of shrinkable film, an expansible film and a pressure sensitive adhesive layer for setting the object;
fixing edges of the pressure sensitive adhesive sheet for producing chip;
dicing the object into chips, and
shrinking the shrinkable film to thereby expand chip spacings.
The pressure sensitive adhesive sheet for producing chip of the present invention is suitably used in the above process and comprises a zone for setting an object to be diced including an expansible film and a pressure sensitive adhesive layer for setting the object and a shrinkage zone including at least one layer of shrinkable film, wherein the shrinkage zone is arranged at least outside the zone for setting the object.
Preferred pressure sensitive adhesive sheet for producing chip is, for example, one wherein the pressure sensitive adhesive layer for setting the object, the shrinkable film and the expansible film are laminated in this order as shown in FIG. 1 or one wherein the pressure sensitive adhesive layer for setting the object, the expansible film and the shrinkable film are laminated in this order as shown in FIG. 2.
In the present invention, it is preferred that the expansible film have an elastic modulus of less than 1xc3x97109 N/m2 and that the pressure sensitive adhesive layer for setting the object be composed of a radiation curable pressure sensitive adhesive.
Further, it is preferred that the shrinkable film and the expansible film are laminated via an adhesive layer having an elastic modulus of at least 1.0xc3x97105 N/m2.